Transition Metal Containing Aluminophosphate Microporous Compounds: Syntheses And Characterizations

Microporous materials with regular microporous structures have been extensively used in many industrial processes such as catalysis, adsorption and separation, as well as in new applications of electronics, magnetism, chemical sensors, medicine, etc. Therefore, research works concerned with the structure design, synthesis, characterization research and exploiration of novel synthetic route, have arisen wide attentions. Aluminophosphate microporous compounds have been extensively studied due to their rich structural architectures and important applications in catalysis, absorption and separation. Now, aluminophosphate microporous compounds have become to an important family of microporous materials. Particularly, transition metal containing aluminophosphate microporous compounds have exhibited special redox and catalytic properties because of the creation of acid sites and redox centers, as well as photoluminescence properties, electronic conductivity and magnetic properties.Herein, we mainly focus on the preparation and characteristics of the transition-metal containing aluminophosphate microporous compounds. Main achievements are as follow:1. A Mg-containing aluminophosphate molecular sieve [C₆H₁₆N₂][Mg₂Al₃P₅O₂₀] (denoted MgAPO-CJ60) with a new zeotype structure has been synthesized by using1,2-diaminocyclohexane (DACH) as the template under hydrothermal conditions. Its structure is constructed by the strict alternation of Al(Mg)O₄ and PO₄ tetrahedra, which contains 8-ring channels along the [100] and [010] directions. It is a new member of ABC-6 family, with the connection mode of ABBCCACCBB(A). The inorganic framework is featured by the d6r and can cages connected to form d6r-can-d6r units, which are further cross-linked to each other via bridging O atoms to form eri (4⁶4⁶6²6³8⁶) and cha (4⁶4⁶6²8⁶) cavities. The template molecules are located in the eri and cha cavities to balance the positive charge of the framework.2. A Zn-containing aluminophosphate [C₆H₁₆N₂][Zn₂Al₃P₅O₂₀],with novel zeolitic topology (designated as ZnAPO-CJ61) has been hydrothermally prepared by using 1,2-diaminocyclohexane as the template in a novel zeolitic topology. Its inorganic structure is constructed from strict alternation of PO₄ and AlO₄ (ZnO₄) tetrahedra to form ionic framework [Zn₂Al₃P₅O₂₀]^2-. Elemental analysis shows that the Zn/Al ratio is 2/3. Structural analysis of ZnAPO-CJ61 indicates the existence of two dimensional 8-ring channels along the [100] and [010] direction, respectively. Notably, ZnAPO-CJ61 is a new member of ABC-6 family that it possesses a novel consequence of ABBAACAACCBCCBB(A) along the c axis. The structure of ZnAPO-CJ61 is comprised of d6r, can [4⁶6⁵], gme [4³4⁶6²8³] and a novel cage [4³4⁶4⁶6²6³8³8⁶].3. A series of transition metal containing aluminophosphates M₂Al₄(PO₄)₆[Ni(DETA)₂] (M=Mn,Zn and Co)with CHA zeotype have been prepared under the hydrothermal conditions. The linkages of AlO₄ (MO₄) tetrahedra and PO₄ tetrahedra through vertex oxygen atoms form the inorganic framework [Mn₂Al₄(PO₄)₆]^2-. Notably, Al and Mn atoms share the same site, and the Mn/Al ratio in MnAPO-CHA is 1/2. Self-assembled nickel complexes are located in the cha to neutralize the negative charge of the framework.4. A series of transition metal containing aluminophosphates MAl(PO₄)₂[(C₂H₅)₂NH₂] (M=Mn, Fe, Co, Zn) have been prepared under the hydrothermal conditions in the presence of diethylamine molecules. Their frameworks are analogous to zeotype CHA structure in which 50% of the aluminum sites are replaced by transitional-metal ions. These compounds show photoluminescent properties, but the emission intensities are different due to the different transitional metals. Magnetic measurements reveal that there is very weak antiferromagnetic interaction among the metal centers of MAl(PO₄)2[(C₂H₅)₂NH₂] (M=Mn,Fe, Co).5. In an attempt to synthesize microporous materials towards a green-chemistry way, we investigate the syntheses of transition metal containing aluminophosphate microporous compounds by a low-cost approach through recycling waste mother-liquors of two layered aluminophosphates Mu-4 and AlPO-IM prepared in the Al(i-PrO)₃-H₃PO₄-Tem-TEG system (Tem: diethylamine or imidazole, TEG: triethylene glycol). A Co-containing aluminophosphate [C₈H₂₄N₂][Al₈Co₂P₁₀O₄₀] (denoted CoAPO-CJ51 ) was obtained with the addition of Co2+ ions into the mother-liquor of Mu-4. Its structure is analogous to zeotype GIS with 20% occupancy by Co2+ ions in the metal site, and the protonated diethylamine molecules locate in the 8-ring channels. Co-containing aluminophosphate [C₃H₅N₂][Al₂CoP₃O₁₂] (denoted CoAPO-CJ52 ) was obtained with the addition of Co2+ ions into the mother-liquor of AlPO-IM. Its structure is analogous to zeotype LAU with 20% occupancy by Co2+ ions in the metal site, and the protonated imidazole molecules locate in the 10-ring channels.6. Aluminophosphate [Cu(en)2] [Al₆P₆O₂₄(OH)₂](designated as AlPO-CJ53) with the AWO topology has been synthesized under the hydrothermal condition by using [Cu(en)₂]²⁺ cations as the template instead of organic amines. Temperature-variation XRD analysis indicates its transformation from AlPO-21 (AWO) to CuO@AlPO₄-25 (ATV).